Certain porous particles have a wide variety of uses in the chemical arts. For example, hydrophobic oxide materials are widely used for different gas- and liquid-phase separation processes. A particularly widely used example is silica gel, which is known to be useful for many applications including chromatography, adsorption and purification of biologically active compounds and medicinal preparations, and stabilization of multi-component systems. However, the surface properties of native silica are not always appropriate for the desired application. Surface modification can be achieved, for example, by transformation of hydrophilic silanol groups into hydrophobic groups, which generally lowers the affinity of modified silica with respect to water. In general, known hydrophobic treatments of silica gel are designed to make both the external surface and the internal pore surface hydrophobic.